BADBLOCKS(8) System Manager's Manual BADBLOCKS(8)
NAME
badblocks - search a device for bad blocks
SYNOPSIS
badblocks [ -svwnfBX ] [ -b block_size ] [ -c blocks_at_once ] [ -d
read_delay_factor ] [ -e max_bad_blocks ] [ -i input_file ] [ -o out-
put_file ] [ -p num_passes ] [ -t test_pattern ] device [ last_block ] [
first_block ]
DESCRIPTION
badblocks is used to search for bad blocks on a device (usually a disk
partition). device is the special file corresponding to the device (e.g
/dev/hdc1). last_block is the last block to be checked; if it is not
specified, the last block on the device is used as a default.
first_block is an optional parameter specifying the starting block num-
ber for the test, which allows the testing to start in the middle of the
disk. If it is not specified the first block on the disk is used as a
default.
Important note: If the output of badblocks is going to be fed to the
e2fsck or mke2fs programs, it is important that the block size is prop-
erly specified, since the block numbers which are generated are very de-
pendent on the block size in use by the file system. For this reason,
it is strongly recommended that users not run badblocks directly, but
rather use the -c option of the e2fsck and mke2fs programs.
OPTIONS
-b block_size
Specify the size of blocks in bytes. The default is 1024.
-c number of blocks
is the number of blocks which are tested at a time. The default
is 64.
-d read delay factor
This parameter, if passed and non-zero, will cause bad blocks to
sleep between reads if there were no errors encountered in the
read operation; the delay will be calculated as a percentage of
the time it took for the read operation to be performed. In other
words, a value of 100 will cause each read to be delayed by the
amount the previous read took, and a value of 200 by twice the
amount.
-e max bad block count
Specify a maximum number of bad blocks before aborting the test.
The default is 0, meaning the test will continue until the end of
the test range is reached.
-f Normally, badblocks will refuse to do a read/write or a non-de-
structive test on a device which is mounted, since either can
cause the system to potentially crash and/or damage the file sys-
tem even if it is mounted read-only. This can be overridden us-
ing the -f flag, but should almost never be used --- if you think
you're smarter than the badblocks program, you almost certainly
aren't. The only time when this option might be safe to use is
if the /etc/mtab file is incorrect, and the device really isn't
mounted.
-i input_file
Read a list of already existing known bad blocks. Badblocks will
skip testing these blocks since they are known to be bad. If in-
put_file is specified as "-", the list will be read from the
standard input. Blocks listed in this list will be omitted from
the list of new bad blocks produced on the standard output or in
the output file. The -b option of dumpe2fs(8) can be used to re-
trieve the list of blocks currently marked bad on an existing
file system, in a format suitable for use with this option.
-n Use non-destructive read-write mode. By default only a non-de-
structive read-only test is done. This option must not be com-
bined with the -w option, as they are mutually exclusive.
-o output_file
Write the list of bad blocks to the specified file. Without this
option, badblocks displays the list on its standard output. The
format of this file is suitable for use by the -l option in
e2fsck(8) or mke2fs(8).
-p num_passes
Repeat scanning the disk until there are no new blocks discovered
in num_passes consecutive scans of the disk. Default is 0, mean-
ing badblocks will exit after the first pass.
-s Show the progress of the scan by writing out rough percentage
completion of the current badblocks pass over the disk. Note
that badblocks may do multiple test passes over the disk, in par-
ticular if the -p or -w option is requested by the user.
-t test_pattern
Specify a test pattern to be read (and written) to disk blocks.
The test_pattern may either be a numeric value between 0 and
ULONG_MAX-1 inclusive, or the word "random", which specifies that
the block should be filled with a random bit pattern. For
read/write (-w) and non-destructive (-n) modes, one or more test
patterns may be specified by specifying the -t option for each
test pattern desired. For read-only mode only a single pattern
may be specified and it may not be "random". Read-only testing
with a pattern assumes that the specified pattern has previously
been written to the disk - if not, large numbers of blocks will
fail verification. If multiple patterns are specified then all
blocks will be tested with one pattern before proceeding to the
next pattern.
-v Verbose mode. Will write the number of read errors, write errors
and data- corruptions to stderr.
-w Use write-mode test. With this option, badblocks scans for bad
blocks by writing some patterns (0xaa, 0x55, 0xff, 0x00) on every
block of the device, reading every block and comparing the con-
tents. This option may not be combined with the -n option, as
they are mutually exclusive.
-B Use buffered I/O and do not use Direct I/O, even if it is avail-
able.
-X Internal flag only to be used by e2fsck(8) and mke2fs(8). It by-
passes the exclusive mode in-use device safety check.
WARNING
Never use the -w option on a device containing an existing file system.
This option erases data! If you want to do write-mode testing on an ex-
isting file system, use the -n option instead. It is slower, but it
will preserve your data.
The -e option will cause badblocks to output a possibly incomplete list
of bad blocks. Therefore it is recommended to use it only when one wants
to know if there are any bad blocks at all on the device, and not when
the list of bad blocks is wanted.
AUTHOR
badblocks was written by Remy Card <Remy.Card@linux.org>. Current main-
tainer is Theodore Ts'o <tytso@alum.mit.edu>. Non-destructive
read/write test implemented by David Beattie <dbeattie@softhome.net>.
AVAILABILITY
badblocks is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
SEE ALSO
e2fsck(8), mke2fs(8)
E2fsprogs version 1.47.2 January 2025 BADBLOCKS(8)
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